// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <algorithm>

#include "base/format_macros.h"
#include "base/logging.h"
#include "base/strings/stringprintf.h"
#include "net/http/http_byte_range.h"

namespace {

const int64_t kPositionNotSpecified = -1;

} // namespace

namespace net {

HttpByteRange::HttpByteRange()
    : first_byte_position_(kPositionNotSpecified)
    , last_byte_position_(kPositionNotSpecified)
    , suffix_length_(kPositionNotSpecified)
    , has_computed_bounds_(false)
{
}

// static
HttpByteRange HttpByteRange::Bounded(int64_t first_byte_position,
    int64_t last_byte_position)
{
    HttpByteRange range;
    range.set_first_byte_position(first_byte_position);
    range.set_last_byte_position(last_byte_position);
    return range;
}

// static
HttpByteRange HttpByteRange::RightUnbounded(int64_t first_byte_position)
{
    HttpByteRange range;
    range.set_first_byte_position(first_byte_position);
    return range;
}

// static
HttpByteRange HttpByteRange::Suffix(int64_t suffix_length)
{
    HttpByteRange range;
    range.set_suffix_length(suffix_length);
    return range;
}

bool HttpByteRange::IsSuffixByteRange() const
{
    return suffix_length_ != kPositionNotSpecified;
}

bool HttpByteRange::HasFirstBytePosition() const
{
    return first_byte_position_ != kPositionNotSpecified;
}

bool HttpByteRange::HasLastBytePosition() const
{
    return last_byte_position_ != kPositionNotSpecified;
}

bool HttpByteRange::IsValid() const
{
    if (suffix_length_ > 0)
        return true;
    return (first_byte_position_ >= 0 && (last_byte_position_ == kPositionNotSpecified || last_byte_position_ >= first_byte_position_));
}

std::string HttpByteRange::GetHeaderValue() const
{
    DCHECK(IsValid());

    if (IsSuffixByteRange())
        return base::StringPrintf("bytes=-%" PRId64, suffix_length());

    DCHECK(HasFirstBytePosition());

    if (!HasLastBytePosition())
        return base::StringPrintf("bytes=%" PRId64 "-", first_byte_position());

    return base::StringPrintf("bytes=%" PRId64 "-%" PRId64,
        first_byte_position(), last_byte_position());
}

bool HttpByteRange::ComputeBounds(int64_t size)
{
    if (size < 0)
        return false;
    if (has_computed_bounds_)
        return false;
    has_computed_bounds_ = true;

    // Empty values.
    if (!HasFirstBytePosition() && !HasLastBytePosition() && !IsSuffixByteRange()) {
        first_byte_position_ = 0;
        last_byte_position_ = size - 1;
        return true;
    }
    if (!IsValid())
        return false;
    if (IsSuffixByteRange()) {
        first_byte_position_ = size - std::min(size, suffix_length_);
        last_byte_position_ = size - 1;
        return true;
    }
    if (first_byte_position_ < size) {
        if (HasLastBytePosition())
            last_byte_position_ = std::min(size - 1, last_byte_position_);
        else
            last_byte_position_ = size - 1;
        return true;
    }
    return false;
}

} // namespace net
